From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,T_DKIMWL_WL_MED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id 42D39C433EF for ; Fri, 15 Jun 2018 16:04:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E0F06208B5 for ; Fri, 15 Jun 2018 16:04:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cogentembedded-com.20150623.gappssmtp.com header.i=@cogentembedded-com.20150623.gappssmtp.com header.b="iH6gru1c" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E0F06208B5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=cogentembedded.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965990AbeFOQEv (ORCPT ); Fri, 15 Jun 2018 12:04:51 -0400 Received: from mail-lf0-f65.google.com ([209.85.215.65]:39936 "EHLO mail-lf0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965930AbeFOQEt (ORCPT ); Fri, 15 Jun 2018 12:04:49 -0400 Received: by mail-lf0-f65.google.com with SMTP id q11-v6so15378878lfc.7 for ; Fri, 15 Jun 2018 09:04:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cogentembedded-com.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:organization:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=aPcQvmdLT70aNZA0Mzptu2XsCWgB41l+2K41lyaocjg=; b=iH6gru1cGa6NgbhYEeNKt050iESkt36MbHfl0wvnEz4q7BLtKRbu/GvtuJFt/LDSox Ns7cyCYwZAbCokkkSvBI5jkM+bdgV0F+SojZjnDujEF3a+ZbY7lPtalk62E4FIehvQeO aEm/9OZq3I9pURtydcSFWNCAmOKmmpX2Kt57dOrAOmI8sk+Tg2syg3kN5oEIDLgbdt/x qRmR3vuDzDXkp9QwqVgFNGsnm1Z/hpUo9jsrIPT598KOVq+BPj0rhehInBZXypiLNd2R jvnnC0zl29A/LuBQRYe9jg1Lj4K+/oSrhajiLnkx9+ZPSAGHc9AQ1T5dgnDKjZ6AJBLC tM/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:organization :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=aPcQvmdLT70aNZA0Mzptu2XsCWgB41l+2K41lyaocjg=; b=MA/dgrWtd6F/+0nH63H1+0/pHkkGuaFFZuaVchhX4WhLRId37h5mEZvFt2Si/cMqF9 R2gloLQACqlu4UEYi8YUaTIlAlwog3VdRK0BxcKmpcapuogx0uTG7yAxF2eWouqYtWdf lsWn6ftYIOrU4sIVVZjfPvZM9GxzqSkX+jcfbBNaTfA8v1cLBspPCsJlH+Zg/8zxX3kS YCUGfL5zXv7/lX2HvffxOdZ0dAVm6qoe+SPcv5P+rfOPBuR8xMKthADhAKLDRBLpYy1O 4HbWX2vJz5/rGkIPg4UvhcWH+ixdCiEkMJoGzKQQEo6eUF/dMRCOLRKnCwJmF+1zcrmj KgNA== X-Gm-Message-State: APt69E3UO4NSVDY1IXn+JmgcaR9TzeR1nG9SsH9Z+iSyHEw6bmYacP/6 ce09vVS8IFapXI5Pd8bNsiQ+/9Ow94Y= X-Google-Smtp-Source: ADUXVKIGpoXf4GrtIx3DdmAki9uBe4rXTnKbdGWRFiKNXlm3VHi43z9Bkzcd6Mp7hsMT/A5uCxDiWA== X-Received: by 2002:a19:2c94:: with SMTP id s142-v6mr1643034lfs.121.1529078687606; Fri, 15 Jun 2018 09:04:47 -0700 (PDT) Received: from wasted.cogentembedded.com ([31.173.81.128]) by smtp.gmail.com with ESMTPSA id s18-v6sm1510337ljg.87.2018.06.15.09.04.46 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Jun 2018 09:04:46 -0700 (PDT) Subject: Re: [PATCH] arch/sh: use slow path for get_user_pages_fast() on SMP To: Thomas Petazzoni , Yoshinori Sato , Rich Felker , linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org References: <20180615155237.8166-1-thomas.petazzoni@bootlin.com> From: Sergei Shtylyov Organization: Cogent Embedded Message-ID: <474bbdcc-d78f-faa0-b2c3-3650cc870b36@cogentembedded.com> Date: Fri, 15 Jun 2018 19:04:45 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20180615155237.8166-1-thomas.petazzoni@bootlin.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-MW Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello! On 06/15/2018 06:52 PM, Thomas Petazzoni wrote: > The fast path of get_user_pages_fast() disables IRQs and then does: > > - gup_pud_range() > - gup_pmd_range() > - gup_pte_range() > - flush_dcache_page() > > However, flush_dcache_page() makes a smp_call_function(), and using > smp_call_function() when IRQs are disabled is not allowed. > > In order to work around this problem, this commit prevents the fast > path from get_user_pages_fast() from being used on SMP, and directly ^^^^ of? Else it sounds a bit tautological... > uses the slow path, which doesn't disable interrupts. > > Fixes the following warning when get_futex_key() is called: > > WARNING: CPU: 1 PID: 410 at kernel/smp.c:416 smp_call_function_many+0x1fc/0x2ac > Modules linked in: > > CPU: 1 PID: 410 Comm: wdc-pfmu-test Tainted: G O 4.13.0-00035-g0d3023c733a0-dirty #363 > task: 97d9a120 task.stack: 97d2e000 > PC is at smp_call_function_many+0x1fc/0x2ac > PR is at smp_call_function_many+0x1e2/0x2ac > PC : 88071fd4 SP : 97d2fcd4 SR : 400080f1 > TEA : c06d6840 > R0 : 000000f0 R1 : 00000002 R2 : 00000000 R3 : 8849c89c > R4 : 886d62c4 R5 : 886d62c4 R6 : 886db928 R7 : 884a9dec > R8 : 00000000 R9 : ffffffff R10 : 8844667c R11 : 29ee9000 > R12 : 8844667c R13 : 00000001 R14 : 97d2fcd4 > MACH: 000177e7 MACL: 0000018c GBR : 295742d0 PR : 88071fba > > Call trace: > [<8800fe2c>] sh4_flush_dcache_page+0x0/0xa4 > [<880720a2>] smp_call_function+0x1e/0x50 > [<8800fe2c>] sh4_flush_dcache_page+0x0/0xa4 > [<8800ecc0>] flush_dcache_page+0x34/0x74 > [<88010d1c>] gup_pte_range+0xd0/0x140 > [<88010e04>] gup_pmd_range+0x78/0xa8 > [<88010c4c>] gup_pte_range+0x0/0x140 > [<88011006>] get_user_pages_fast+0xda/0x130 > [<8806f376>] get_futex_key+0x72/0x3a0 > [<8806f6a4>] futex_wait_setup+0x0/0x10c > [<88055a08>] __rcu_read_unlock+0x0/0x54 > [<880559c8>] __rcu_read_lock+0x0/0x1c > [<88010f2c>] get_user_pages_fast+0x0/0x130 > [<8806f6de>] futex_wait_setup+0x3a/0x10c > [<8806f6a4>] futex_wait_setup+0x0/0x10c > [<8806f852>] futex_wait+0xa2/0x1b8 > [<8806f6a4>] futex_wait_setup+0x0/0x10c > [<88071c00>] smp_call_function_single+0xac/0x108 > [<8800e908>] cache_noop+0x0/0xc > [<8800e908>] cache_noop+0x0/0xc > [<88071018>] do_futex+0x108/0x8f8 > [<880bdfe4>] finish_fault+0x38/0x70 > [<880bdff2>] finish_fault+0x46/0x70 > [<880bf212>] handle_mm_fault+0x2f6/0x954 > [<880bf21a>] handle_mm_fault+0x2fe/0x954 > [<88030e64>] resched_curr+0x54/0x6c > [<8832be9e>] _raw_spin_lock_irqsave+0xa/0x18 > [<880718dc>] SyS_futex+0xd4/0x124 > [<8801488e>] SyS_clone+0x16/0x24 > [<8800727e>] syscall_call+0x18/0x1e > [<88071808>] SyS_futex+0x0/0x124 > > Signed-off-by: Thomas Petazzoni [...] MBR, Sergei